The present invention is directed to a rotary pump of the type having two double-lobed rotors rotatable in intermeshing relation on parallel shafts in a pumping chamber, and more specifically to a rotary pump having cutting means on the lobes for comminuting sewage or garbage which might be entrained with the liquid being pumped.
Pumps or compressors of the type having two intermeshing double-lobed rotors are old and well known in the art as evidenced by the U.S. Patent to Messori 4,451,132. However, if the fluid being pumped contains sewage or garbage in the form of solid or stringy material, there is the possibility of the pump becoming clogged or jammed with the solid or fibrous material.
The U.S. Patent to Backstrom 4,637,785 is directed to a rotary pump with a cutter device for contaminated fluids. However, in this case the rotating cutter is separate from the pumping elements and is located adjacent the inlet for the masceration of solid objects to a size suitable for the subsequent passage through the pump.
The U.S. Patents to Poss 4,561,834 and Waters 2,974,700 are both directed to rotary vane pumps having knife edged vanes which cooperate with the edge of the inlet opening to shear-cut any solid material entering through the opening into the pump chamber. The vanes of such pumps slide radially in a rotor with the tips of the vanes engaging the rotor chamber's cylindrical interior surface, thereby causing substantial wear to the vanes with the attendant shortening of the life of the vanes. The vanes are relatively thin plates and are extended beyond the circumference of the rotor to the greatest extent when the vane is passing the inlet opening. The impact associated with shear-cutting can cause damage to the vanes, which also shortens the life of the vanes.